工程规模下碱类型对污泥预处理效果及发酵产酸的影响

Effect of alkali types on sludge pretreatment and its fermentation for acid production in industrial scale

研究了工程规模下3种碱对剩余污泥热碱预处理效果以及厌氧发酵产酸的影响。结果表明,平均进泥浓度为70 g·L^(-1)时,氢氧化钠的预处理效果要优于混碱(Ca(OH)_2:NaOH=4:1)和过氧化钙,处理后污泥中溶解性化学需氧量(SCOD)的平均浓度是预处理前的8.45倍,水解率达到64.26%。但是,使用过氧化钙进行预处理可以有效提高污泥的发酵产酸效果,产酸效率明显优于混碱和氢氧化钠,总挥发性脂肪酸(TVFAs)的平均浓度为7.93 g·L^(-1),产酸率(以COD计)为273.93 mg·g^(-1)VSS,且总酸中乙酸比例达到60.35%;发酵后平均TSS和VSS分别下降了24.42%和47.62%;同时,氨氮(NH_4^+-N)和总磷(TP)浓度最低,其平均浓度分别为286.33 mg·L^(-1)和17.42 mg·L^(-1)。此外,混碱组、过氧化钙组和氢氧化钠组污泥厌氧发酵的净利润分别为229.14、257.37和10.49元·t^(-1)(脱水污泥)。实验结果表明,热混碱和热过氧化钙预处理用于污泥厌氧发酵有望得到广泛的应用。

Effects of alkali types on thermal-alkaline pretreatment of waste activated sludge and its anaerobic fermentation for volatile fatty acids（VFAs） production were studied. Results show that the efficiency of sludge pretreatment by Na OH with the average sludge concentration of 70 g·L^（-1） was higher than those of mixed alkali（Ca（OH）2：NaOH = 4：1） and calcium peroxide（CaO2）. The average concentration of soluble chemical oxygen demand（SCOD） after Na OH pretreatment was 8.45 times that before pretreatment, and the hydrolysis rate reached 64.26%. However, CaO2 pretreatment effectively improved the acid production of sludge fermentation, and its efficiency is obviously higher than those of mixed alkali and NaOH. The average concentrations of TVFAs in the CaO2 group was 7.93 g·L^（-1）, and acid production rates（expressed with COD concentration） was 273.93 mg·g^（-1）VSS.Meanwhile, the ratio of acetic acid in the TVFAs of CaO2 group was 60.35%, and the average total suspended solid（TSS） and volatile suspended solid（VSS） decreased by 24.42% and 47.62%, respectively. The concentrations of NH4~＋-N and TP in the CaO2 group were lowest with their average concentrations of 286.33 mg·L^（-1） and 17.42 mg·L^（-1）,respectively. However, the economic feasibility comparison indicates heat-mixed alkali and heat-CaO2 pretreatments for sludge anaerobic fermentation are promising for widely application, with the net profits of 229.14, 257.37 and10.49 yuan·t^（-1） dewatered sludge for the mixed alkali, CaO2 and NaOH treatment, respectively.